Control apparatus and sensor



\ Oct. 5, 1965 11w. AMOS 3,210,710

CONTROL APPARATUS AND SENSOR Filed April 20, 1962 I 4 Sheets-Sheet l -1-I I m m u 27 1 5 16 INVENTOR. DOUGLAS W AMOS W M a A T TOE/V5 Y Oct. 5,1965 D. w. AMOS 3,210,710

CONTROL APPARATUS AND SENSOR Filed April 20, 1962 4 Sheets-Sheet 2 TOCONTROL APPARATUS AND SENSOR 27 INVENTOR DOUGLAS WAMOS' \Q l l BATTORNEY I TO PENDULUM 4 Sheets-Sheet 3 D. W. AMOS CONTROL APPARATUS ANDSENSOR WARN Oct. 5, 1965 Filed April 20, 1962 T. MWN

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INVENTOR[:\ DOUGLAS W AMOS ATTORNEY Oct. 5, 1965 D. w. AMOS 3,210,710

CONTROL APPARATUS AND SENSOR Filed April 20, 1962 4 Sheets-Sheet 4INVENTOR. DOUGZAS' W AMOS United States Patent 3,210,710 CONTROLAPPARATUS AND SENSGR Douglas W. Amos, Richfield, Minn, assignor toHoneywell Inc., a corporation of Delaware Filed Apr. 20, 1962, Ser. No.189,124 8 Claims. (Cl. 338-68) The present invention is concerned withan improved control apparatus and sensor, particularly adapted for usewith road paving machines.

Roads are commonly surfaced with a surfacing material by means of pavingmachines including a hopper into which the material is deposited and outof which the material is fed, immediately in front of a screed or thelike, to be deposited on the surface to be paved. The screed compactsand smooths the paving material to form a paved road surface. Thus, theheight of the screed is effective to control the height or grade of theresulting paved road.

A type of paving machine of this general construction utilizes afloating screed which freely rests upon the paved surface by virtue ofthe weight of the screed. The angle .of attack of the screed, that isthe attitude of the bottom surface of the screed, determines the heightof the reulting paved surface. More specifically, a paving machine ofthis type is provided with a propulsion unit which includes a pair ofcrawler treads or wheels disposed at opposite sides of the propulsionunit, to move the unit. The forward end of the propulsion unit may beprovided with a hopper to receive the road surfacing material. Thismaterial is then fed out of the rear portion of the propulsion unit,onto the surface to be paved. Thus, as the propulsion unit moves alongthe roadway to be paved, the floating screed, towed behind thepropulsion unit, is pulled over the road paving material and leaves apaved road surface. The floating screed, which is towed by thepropulsion unit, may be towed by means of a pair of forwardly extendingbeams or arms, the forward portions of which are freely pivoted to thepropulsion unit at opposite sides of the unit. The rear ends of thebeams or arms are rigidly atached to the screed. Thus, as the height ofthe forward portion (or an intermediate section) of the beams isvertically raised or lowered, the angle of attack of the screed Varies.The raising of the tow beams causes the vertical height of the roadbedto increase, while a lowering of the tow beam causes a change in angleof attack such that the surface of the roadbed is lowered.

A control system has ,been originated to automatically control theattitude of the screed, and to thus provide a road surface having aheight established by a predetermined height datum which has beenpositioned along the surface to be paved. This system utilizes a pair ofcontrol apparatus, including transducers in the form of potentiometerswhose wipers are controlled by the sensors, one of the apparatus being aheight control disposed on one of the beams, the other being a pendulumslope control. A control apparatus of this type is described in thecopending application of Richard C. Flom, Serial No. 144,667, filedOctober 12, 1961.

While the apparatus of my invention is shown used with an asphalt pavingmachine, it may also be used with other devices and machines such asconcrete paving machines, formless paving machines, or subgradingmachines. When the apparatus of my invention is mounted in a generallyvertical attitude, it may be used to follow a datum, for example tosteer a machine.

My invention is directed to the arrangement of the height controlapparatus and sensor, adapted to be selectively located on one or theother or both of the tow beams of the screed, to thus be controlled by aheight datum which has previously been placed along the surface to bepaved. This height control apparatus and sensor includes a followersensor which may ride on, or cooperate with, a taut wire or a string, ormay cooperate with the existing road surface adjoining the road surfacethen being formed. My height control apparatus and sensor, also called afollower sensor, includes a control potentiometer, the wiper of which iscontrolled and moved by the sensor which follows the guide wire orstring. This sensor may also be a ski-type shoe attachment for followingan existing adjoining road surface. Vertical motion of a portion of thesensor is translated into rotary motion which is used to position thewiper of the potentiometer.

The housing of my control apparatus is divided into two sections, one ofwhich is sealed and includes the potentiometer. Thus, reliability ofoperation of the potentiometer is achieved. The potentiometer wiper ismounted on a shaft which extends from one compartment to the other,within the housing, by means of a seal preventing the passage of dustand the like into the sealed compartment housing the potentiometer. Thesensor is attached to the shaft by means of a snap-on connection whichallows the sensor to be knocked off, without damage, if it hits anobstacle.

An electrical interlock, including the snap-on connection as a portionthereof, is provided, such that a warning signal or a shutdown of thepaving machine is achieved if the sensor is inadvertently knocked off.

Furthermore, to accommodate unusual degrees of movement of the sensor,the snap-on connection is coupled to the first mentioned shaft by meansof an override mechanism. This override mechanism allows thepotentiometer wiper to move to a limit of its range, where it hits astop, with additional movement of the sensor taken up in the overridemechanism without applying undue pressure to the potentiometer wiper,which is then positioned against the stop.

Furthermore, my control apparatus sensor, which may be positioned oneither side of a paving machine, is provided with adjustable springloading or biasing means which cooperates with the first mentioned shaftand biases the shaft for rotation in one direction 'or the other,depending upon the side of the machine with which the unit is used.Thus, the spring biasing determines the amount of force which must beovercome by the sensor, riding on the height reference datum, beforemovement of the potentiometer wiper is achieved.

My invention will be apparent to those skilled in the art upon referenceto the following specification, claims and drawings, of which:

FIGURE 1 is a view of a paving machine of the floated screed type,

FIGURE 2 is a simplified showing of portions of the paving machine ofFIGURE 1, showing my improved control apparatus and sensor as it relatesto the structure of the paving machine,

FIGURE 3 is a schematic representation of an electronic control systemwith which my improved control apparatus and sensor may be utilized,

FIGURE 4 is a side view of my control apparatus and sensor, with aportion of the outer case broken away to show a sectional view ofelements within the housing,

FIGURE 5 is a view of the override mechanism and the spring loading orbiasing mechanism,

FIGURE 6 is a view of the potentiometer construction,

FIGURE 7 is a view of the override mechanism, taken from the sideopposite the showing of FIGURE 5 and showing an alternate positionthereof,

FIGURE 8 is a section view of the snap-on-connection constructionincluding the electrical interlock, and

FIGURE 9 is a view of the manner of selectively mounting the sensorportion.

Referring specifically to FIGURE 1, reference numeral 10 identifiesgenerally a paving machine having a propulsion unit 11 including ahopper 12 and crawler type threads 13. This propulsion unit 10 includesa motor connected to drive the threads 13, one of which is disposed ateach side of the paving machine 10. The hopper 12 of the paving machineis adapted to receive bituminous material, usually dumped into thehopper by trucks which haul the bituminous material between the roadbedto be paved and the plant which is producing the material. The pavingmachine 10 is adapted to be operated by an operator positioned on thepaving machine, and reference numeral 14 identifies a control boxwhereby the operator may selectively automatically or manually controlthe road surface which is being produced by paving machine 10.

Reference numeral 15 identifies a roadbed which is to be paved and alongwhich a height reference datum 16 'is provided, this height referencedatum consisting of a wire, string, or the like which has beenpreviously placed in position alongside the roadbed 15 at apredetermined height. Reference numeral 17 designates a finished roadsurface which has been produced by the paving machine as it moves in aforward direction, that is to the right as shown in FIGURE 1. Ifdesired, the height datum may also be obtained from a previouslyproduced roadbed mat, for purposes of matching one mat to another.

Reference numeral 20 identifies generally a screed construction which isrigidly attached to a beam 21, pivoted to the propulsion unit at aforward pivot 22. Paving machine 10 of FIGURE 1 is provided with a pairof beams, one of which is positioned at each side of the propulsion unitwith each of the beams pivoted "at its forward end. The attitude of thescreed, that is the angle of attack of the lower surface thereof, may beinitially manually controlled by means of a pair of screed adjustmentscrews 24 and 25 which can be turned by the operator of the pavingmachine to control the angle of attack of the screed. The bituminousmaterial is fed from hopper 12 to a spreader type mechanism 26 which iseffective to spread the bituminous material on the roadbed 15immediately in front of screed 20, where the material is compacted bythe screed into the finished road 17. The screed assembly 20 may includea vibrating mechanism or tamping mechanism as well as a means forheating the bituminous material deposited under and in front of thescreed.

The invention of the above mentioned copending application of Richard C.Flom deals with an improved control apparatus for automaticallycontrolling the screed 20 in a manner to produce a predeterminedfinished road 17. This is accomplished by means including my improvedcontrol apparatus and sensor 27 cooperating with the height datum 16.

Referring now to FIGURE 2, in this figure is shown a simplified view ofthe screed, its supporting beams, their pivot points, a pendulum, and myimproved control apparatus sensor. As in FIGURE 1, the screed assemblyis identified by the reference numeral 20 having a bottom surface 23.Beam 21, having pivot 22, is shown, as is the other beam 31 disposed atthe back side of the paving machine 10, as seen in FIGURE 1. Beam 31 isprovided with a pivot 32. The control apparatus and sensor 27 of theinvention is shown adjustably positioned on beam 21 and in engagementwith the height datum 16. A pendulum 30 is supported on a transversebeam 33 which is pivotally mounted at a pair of upper supports 34, 35associated with the beams 21 and 31 respectively. Thus, as the pivotpoints of beams 21 and 31 move up and down, the beam 33 is maintained intransverse alignment with pivot points 22 and 32. Pendulum 30,responsive to gravity, thus assumes a position indicative of the slopeof beam 33. The height of the pivots 22 and 32 is controlled by a pairof pivot adjusting screws 36 and 37 which are controlled by a pair ofreversible D.C. motors 40 and 41.

As mentioned, screed, assembly 20 floats on the bituminous materialdeposited thereunder and is attached to the propulsion unit 11 by meansof the pivots 22 and 32. Thus, the angle of attack of the bottom surface23 of the screed is controlled by the vertical movement of these pivotpoints. Should the pivot points 22 and 32 be driven in an upwarddirection, the bottom surface 23 of the screed assembly is tilted in anupward direction. Thus, the screed climbs up on top of the greaterthickness of bituminous material which is deposited under the screed.The height of the finished road surface 17 is then increased. Should thepivot points 22 and 32 be lowered, the bottom surface 23 of the screedassembly is tilted in a downward direction and the screed digs into thebituminous material deposited in front of the screed and thus thefinished road surface 17 is reduced in thickness, that is the height isdecreased. Furthermore, the transverse slope of the finished roadsurface 17 may be controlled by raising or lowering the pivots 22 and 32in a differential fashion. Thus, as pivot 22 is lowered, While pivot 32is raised, screen assembly 20 is tilted to raise the righthand end asseen in FIGURE 2, while lowering the lefthand end. The resulting roadsurface 17 is then sloped toward the height datum 16.

Referring now to FIGURE 3, in this circuit is disclosed a schematicdiagram of an electronic circuit by which the paving machine and thusthe finished road surface may be manually or automatically controlled atthe option of the operator of the paving machine. The disclosure ofFIGURE 3 corresponds to a portion of the disclosure of the abovementioned copending application of Richard C. Flom.

This figure discloses two signal channels, one of which is operativewith the pendulum 30 and the other of which is operative with myimproved control apparatus and sensor 27. The outputs of each of thesesignal channels may be selectively connected to control the D.C.reversible motors 40 and 41 under the control of manually operativeswitch means 42.

The basic components of the control system of FIG- URE 3 constitute A.C.bridge circuits 43 and 44, meter drive circuits 45 and 46 connected toindicating meters 47 and 48 respectively, and motor drive circuits 50and 51 which provide reversible polarity D.C. voltage across outputresistors 52 and 53 respectively. The output re sistors 52 and 53 may beselectively connected to either of the motors 40 and 41, depending uponthe position of manual switch 42.

The lower portion of the schematic diagram of FIG- URE 3 discloses theportion controlled by the control apparatus and sensor of the presentinvention. The control apparatus and sensor 27 of FIGURES 1 and 2 ismechanically connected, by means identified by reference numeral 54, tocontrol the position of wiper 55 of potentiometer '56 having aresistance element 5'7. Potentiometer 56 constitutes a portion of theAC. bridge circuit 44 whose input voltage is supplied by means of atransformer 60 having a primary winding connected to a source ofalternating voltage, not shown.

Referring now to FIGURE 4, the improved control apparatus and sensor ofmy invention is disclosed, again identified generally by means ofreference numeral 27. Apparatus 27 can be seen, for example .byreference to FIGURE 6, to be contained within a circular can-likehousing 100, which housing is broken away to disclosethe interiorportions of apparatus 27. The lefthand end of the housing 100, asdisclosed in FIGURE 4, is closed by a cover member 210 1 mounting anelectrical connector 10 2. (The other end of housing is closed :by acover member 103 held in position by a C-ring closure member 104 adaptedto cooperate with a recess formed on the interior surface of the housing1100. As can also be seen in FIGURES 4 and 6, the housing .100 isconnected to support means 105, this support mean-s being identified inFIGURE 2 as that means by which the control apparatus and sensor 127 ismechanically mounted to the beam 21 of the paving machine.

Reference numeral !106 identifies generally the sensor portion of myinvention. Sensor 106 includes a rod 107 defining a center of notationor the axis of the control apparatus and sensor. This rod cooperateswith a snapon connector 6108, including mating member #120 and 121, tofacilitate mechanical mounting of member i106 to means including arotatable shaft 109 connected to pctentiometer wiper 55, by means to bedescribed. Sensor 106 also includes a spaced wire engaging portion 110comprising a rod disposed generally parallel to rod '107 and attached tothe snap-on connection .108 and to the rod 107 by support means 111.This portion 110 of the sensor 106 is the portion which is adapted toengage the datum means 16 of FIGURE 1 to effect rotation of rod 107, andthrough the snap-on connection 108, to effect rotation of shaft .109,and thus rotation of potentiometer wiper '55. Sensor 106 also includes awind compensation counterweight portion 112 comprising a cylinderdisposed on the opposite side of rod .107 from the above mentionedportion 110. The size and spacing of the wind compensation counterweightportion 112 is such as to compensate for not only the weight of portion110, as it affects rotation of rod I107, but also to provide acrosssectional area resisting the effect of wind on the portions i010and its supports 1111 which are disposed on the opposite side of rod.107, remembering that rod '107 defines the center of rotation of thesensor 106.

Referring now to FIGURE 8, the snap-on connection 108 is shown ingreater detail, and is seen to include mating mechanical couplingmembers 120-121 to physically mount the sensor 106 with respect to theremaining portions of the control apparatus as disclosed in FIGURE 1.Coupling members i120 and F121 preferably carry mating positioning lug-sor the like to allow only one attitude of coupling of coupling members.Member .120 is rotatably mounted in the cover member 103 and carries apair of bolts or rivets 122 and 123 connected to conductors 124 and 125respectively and functioning as electrical terminals. Bolts 122 and 123are mounted within the memher 120 by means of insulating bushings tothus insulate the bolts from member 120. The interior portion of thesnap-on connection 108 includes a bridging electrical contact 2 26which, with sensor 106 mounted on member 120, completes an electricalconnection from conductor L124 through bolt 122, contact 226, and bolt#123 to electrical conductor 125.

In FIGURE 1, a terminal 127 is seen to lead the conductor 1125 throughan interior wall 126 to a further conductor 128. The terminal .127 isled through the wall #126 and is insulated from the wall 126 by meansincluding a sealing member 1 29, this sealing member preventing thepassage of dust and the like between the two compartments of the controlapparatus identified generally by means of reference numerals .130 and.131.

Conductor (124 of FIGURE 8 is likewise provided with a terminal similarto terminal 127 and thus conductors 124 and -125 are led to terminals ofconnector 102 at the interior surface of wall 101, these terminals beingthe interior projecting portions of the connector i102, as shown. Acable, mating with the exterior portion of connector .102, connectsconductors 124 and 125 to electrical control means, not shown. Forexample, the closed switch rep-resented by the bolt 122, contact 226 andbolt 123 may be electrically connected in series with the circuitcontrolling the forward motion of the machine. For example, the clutchesto drive wheels or the like from the internal combustion engine poweringthe paving machine of FIGURE -1 may be rendered inoperative. As analternative, this closed switch may be connected into an alarm circuitto sound an alarm or to flash an alarm light 6 to indicate to the pavingmachine operator that the sensor 106 has accidentally become disengaged,for example, by striking an obstruction location in the vicinity of thedatum 16.

As has been mentioned, the position of potentiometer wiper 55 iscontrolled by the position of sensor 106. P otentiometer 56 is mountedon a mounting member 132 which in turn carries three terminals 133 (seeFIGURE 6) adapted to be connected to the resistance end terminals and tothe wiper of the potentiometer assembly. The terminals .133 are in turnconnected to the interior portions of connector 102. The above mentionedcable connects the potentiometer assembly to the control system of FIG-URE 3. Referring to FIGURE 3, the reference numerals 134, 135 and .136designate the conductors of the potentiometer assembly which areconnected to the electronic control system of FIGURE 3.

Turning now to the interior construction of the control apparatus, whichincludes the two compartments 130 and :131, these compartments areseparated by the wall 126, including a sealing O-r-ing !137. 'In theprocess of assembly, the cover member 103 is positioned by' means ofpositioning lug 138 (as seen in FIGURE 4) and the inside diameter of thehousing. 'Shorter lugs 139 and 140 are seen in FIGURE 5. Each of theselugs includes a mating coil spring 141. Cover member 10 3 is forced tothe interior of housing 100 such that C-ring 104 may engage groove 100.This action causes the interior wall :126 to be forced into engagementwith a lip 242 formed on the interior surface of housing 100 to thusform the two interior compartments .130 and 131.

Shaft 109 is journalled in bearings 142 and 143 and is then led throughwall 126 by means including a flexible boot 144. The lefthand end ofboot 144 is connected to a collar member 145 fixed to wall portion 126.The righthand end of boot 144 is connected to the sleeve 146, whichsleeve is fixed to shaft 109. Sleeve 146 includes, as an integralportion thereof, a disc 147 which is adapted to be spring biased againstrotation in one direction or the other by means of a spring 148. Theposition of this spring is controlled by a lever 149 which, through apivot 150, is connected to a manual actuator 151 cooperating with a pairof stops 152 and 153 (also see FIGURE 5 Thus, disc 147 rotates withshaft 190. At the lower portion of disc 147 is positioned a drive pinwhich cooperates with an override mechanism designated generally bymeans of reference numeral 161.

Override mechanism 161 is the mechanism by which the sensor 106 isconnected to shaft 109. Sensor 106, mounted by means of snap-onconnection 108, causes rotation of member 120 and thus also causesrotation of a shaft 162 which is disposed within a collar 163. Bothcollar 163 and shaft 162 are fixed to member 120 to rotate therewith.

Loosely disposed or pivoted on member 163 are two drive links and 171,which are interconnected by means of a spring 172, see FIGURES 4, 5 and7. The construction of this aspect of my invention can be seen moreclearly in FIGURE 7 wherein the shape of the links 171 and 172 can beseen. Link 171 is provided with a lower arm 173 cooperating with thedrive pin 160 of disc 147. Drive link 172 is likewise provided with alower arm 1'74 which cooperates with the drive pin 160, pin 160 beingcaptured between arms 173 and 174. Each of the links 171 and 172 isprovided with upper arms 175 and 176 respectively, these upper armscooperating with and capturing a further drive pin 177 between the arms175 and 176. Pin 177 is carried by a rotatable disc-like member 180which is fixed to shaft 162 so as to rotate with this shaft.

With this construction in mind, the rotation of follower sensor 106about its axis (rod 107) and the manner in which shaft 109, and thuspotentiometer 56, is controlled will be considered. With the apparatusas disclosed in FIGURE 4, manual control member 151 is positioned so asto engage stop 153 (see FIGURE Disc 147 is therefore biased to aclockwise position, as viewed from the follower sensor, the view ofFIGURE 7. Thus, potentiometer wiper 55 of potentiometer 55 is biased toits extreme lefthand position, to engage stop 190, the view of FIGURE 6.Likewise, sensor 106 is tilted from a true vertical position such thatthe windage and counterweight portion 112 leads the portion 110. Thus,control member 151, set as shown in FIGURE 4, is set as it would be whenthe control apparatus and sensor 27 is mounted on the left side of thepaving machine.

When the control apparatus is mounted on the right side of the pavingmachine, as seen in FIGURE 1, then the manual control member 151 isshifted so as to engage stop 152. This causes spring 148 and lever 149to shift such that lever 149 also engages stop 152. With this setting ofmember 151, follower sensor is tilted from the true vertical positionwith the windage and counterweight member 112 again leading member 110,the leading attitude of member 112 being related to the control apparatus and sensor 27 as it is mounted on the right side of the pavingmachine of FIGURE 1.

In other words, manual control member 151 and sensor 106 are both tiltedfrom the true vertical, but they are tilted in opposite directions. Thesense or attitude of this tilt is reversed when the unit is shifted fromone side of the paving machine to the other.

FIGURE 9 shows a partial view of the connector member 120 which carriesa positioning pin 200 mating with notches 201 and 202 formed on member121. Notches 201 and 202 are spaced at 90 degrees. When control member151 is as shown in FIGURE 4, notch 201 coopcrates with pin 200, asshown. When control member 151 is shifted to engage stop 152, the sensor106 is removed and replaced in position, rotated 90 degrees, with notch202 cooperating with pin 200.

Assuming that the control apparatus and sensor 27 is mounted on the leftside of the paving machine, the vertical height of unit 27 is adjustedto produce a midposition of wiper 55. Subsequent changes in its verticalposition, as the paving machine encounters irregular terrain, causes theportion 110 of the sensor 106 to be raised or lowered, causing rotationof rod 107. Rotation of this rod causes rotation of shaft 162 by virtueof the rotation of coupling members 120-121. In this manner drive pin177 is caused to rotate about the axis of rod 107 and shaft 109. Thisrotation transmits a force to the arm 175 or 176 of the drive links 171and 172 (depending upon the direction of this rotation). As one of thesedrive links rotates, for example link 176 rotates in a clockwisedirection as seen in FIGURE 7, this rotation is transmitted to link 171through spring 172. Thus, link 171 likewise rotates in a clockwisedirection, and by virtue of its lower arm 173, this clockwise rotationis transferred to drive pin 160 fixed to disc 147. Disc 147 rotates andcauses clockwise rotation of rod 109 and potentiometer wiper 55.

It will be remembered that the apparatus as shown in FIGURE 7 isdisposed with the manual control member 151 positioned such that wiper55 is biased toward its lefthand extremity, that is toward engaging stop190. Thus, the above described rotation of rod 109 causes the wiper tomove from a center position toward stop 190. As this rotation continues,the point is reached where stop 190 is engaged. At this point, overridemechanism 161 functions to prevent undue stress being applied to thepotentiometer construction. Further clockwise movement of drive link 172(as seen in FIGURE 7), for example to the dotted line position of FIGURE7, causes stress to be built up within spring 172. However, pin 160 doesnot rotate beyond the position where potentiometer wiper engages stop190 by virtue of the resilient coupling of S clockwise rotation of theshaft 162 as viewed in FIGURE 7, counterclockwise rotation of this shaftcauses rotation of the potentiometer wiper from a center position, as'shown in FIGURE 6, toward stop 191, its extreme righthand position,whereupon continued rotation of drive link 172 is interrupted whiledrive link 171 continues to rotate in a counterclockwise direction, thisadditional movement being taken up by spring 172.

From the above description, it can be seen that I have provided animproved control apparatus and sensor particularly adapted for use inthe automatic control of a road paving machine.

Modifications of the present invention will be apparent to those skilledin the art and it is thus intended that the scope of the presentinvention be limited to the scope of the appended claims.

I claim as my invention:

1. A follower sensor for use with a land vehicle carrying aninstrumentality which is movable relative to the vehicle, whichinstrumentality is to be maintained at a controlled height relative toan established land based reference datum, the sensor comprising; ahousing adapted to be mounted on the vehicle and movable with theinstrumentality, a rotatable shaft mounted within said housing, outputmeans controlled by said shaft to provide an output dependent upon theposition of rotation of said shaft; follower means having a firstportion mechanically and detachably secured to said shaft, a secondportion spaced from said first portion and rigidly attached thereto,said second portion being adapted to cooperate with the reference datumand to produce rotation of said shaft, and a third portion spaced fromsaid first portion generally opposite said second portion, said thirdportion being constructed and arranged to constitute means tocounterbalance said follower means and to compensate for wind resistanceand the like tending to affect said follower means; and electricalcircuit means adapted to be electrically connected through thedetachable connection of said first portion to said shaft, said circuitmeans constituting control means effective in the event said followermeans is mechanically detached from said shaft.

2. A follower sensor for use with a road paving machine having a movablepaving instrumentality adapted to be controlled in accordance with apre-established datum, and having; electrical control means havingoutput means adapted to control the position of the instrumentality,comprising; a housing adapted to be mounted on the machine and to bemovable with movement of the instrumentality, a shaft rotatably mountedwithin said housing, a potentiometer having a movable wiper connected tosaid shaft and movable therewith, means adapted to connect saidpotentiometer in controlling relation to the electrical control means, asnap-on mechanical coupling mounted on said shaft, a follower sensormechanically mounted on said shaft by virtue of said snap-0n coupling tofacilitate the accidental striking and mechanical disengagement of saidfollower sensor, said follower sensor being adapted to follow the datumto cause rotation of said shaft and a resulting movement of theinstrumentality and said housing, and further electrical circuit meansincluding said snap-on coupling and effective to be electricallyactuated upon accidental disengagement of said follower sensor.

3. In combination; a hollow cup-shaped housing hav ing an open end and aclosed end, an electrical connector mounted in said closed end, a firstwall within said housing positioned generally normal to the axis of saidhousing and dividing said housing into a first and a second compartment,a rotatable shaft mounted in said first wall to extend between saidfirst and second compartments generally parallel to the axis of saidhousing, a potentiometer mounted in said first compartment with thewiper thereof connected to be moved by rotation of said shaft,electrical conductors connecting said potentiometer to said electricalconnector, a closure wall mounted at the open end of said housing, asnap-on mechanical connection rotatably mounted in said closure wall andincluding electrical switch means mounted on said snap-on connection, afollower sensor mounted on said snap-on connection and adapted when somounted to actuate said electrical switch means, an override mechanismwithin said second compartment connecting said snap-on connection tosaid shaft to limit the degree of rotation of said shaft as said snap-onconnection rotates, and electrical conductors connecting said electricalswitch means to said electrical connector.

4. In combination; a hollow cup-shaped housing having an open end and aclosed end, an electrical connector mounted in said closed end, a firstwall posoitioned within said housing generally normal to the axis ofsaid housing and dividing said housing into a first sealed compartmentand a second compartment, a rotatable shaft mounted by virtue of asealed support in said first wall to extend between said first andsecond compartments generally parallel to the axis of said housing, apotentiometer mounted in said first compartment with the wiper thereofconnected to be moved by rotation of said shaft, electrical conductorsconnecting said potentiometer to said electrical connector, a closurewall mounted at the open end of said housing, .a snap-on mechanicalconnection rotatably mounted in said closure wall and includingelectrical switch means, a follower sensor mounted on said snaponconnection and adapted when so mounted to actuate said electrical switchmeans, .a mechanical override mechanism within said second compartmentconnecting said snap-on connection to said shaft to limit the degree ofrotation of said shaft as said snap-on connection rotates, andelectrical conductors connecting said electrical switch means to saidelectrical connector and including sealed portions extending throughsaid first wall.

5. In combination; a hollow cup-shaped housing having an open end and aclosed end, an electrical connector mounted in said closed end, a firstwall positioned Within said housing generally normal to the axis of saidhousing and dividing said housing into a first and a second compartment,a rotatable shaft mounted in said first wall to extend between saidfirst and second compartments generally parallel to the axis of saidhousing, a potentiometer mounted in said first compartment with thewiper thereof connected to be moved by rotation of said shaft,electrical conductors connected said potentiometer to said electricalconnector, a closure wall mounted at the open end of said housing, asnap-on mechanical connection rotatably mounted in said closure wall andincluding electrical switch means, a follower sensor mechanicallymounted on said snap-on connection and adapted when so mounted toactuate said switch means, a mechanical override mechanism within saidsecond compartment mechanically connecting said snap-on connection tosaid shaft to limit the degree of rotation of said shaft as said snap-onconnection rotates, electrical conductors connecting said switch meansto said electrical connector, and directional spring loading meansconnected between said housing and said shaft and selectively adjustableto spring bias said shaft for rotation in one direction or the other tothus establish a force which must be overcome by said follower sensor toachieve movement of said shaft and said potentiometer wiper.

6. A follower sensor for use with a road paving machine having a screedassembly to form a road surface, with a portion of the screed assemblybeing generally vertically movable, the sensor comprising; a housingadapted to be mounted on the screed portion so as to move vertically asthe screed portion moves, a rotatable shaft mounted within said housing,a potentiometer having a wiper controlled by rotation of said shaft,stop means to limit rotation of said wiper, override mechanism mountedon said shaft, a snap-on mechanical connection mounted on said overridemechanism, said override mechanism functioning to limit the rotation ofsaid shaft and said potentiometer wiper as said snap-on connectionrotates, a follower member adapted to cooperate with generallyhorizontal datum means, and means removably mounting said followermember on said snap-on connection.

7. A follower sensor for use with a road paving machine having a screedassembly to form a road surface, with a portion of the screed assemblybeing generally vertically movable, and electrical control meansconnected to control the vertical position of the screed portion; ahousing adapted to be mounted to move as the screed portion moves, arotatable shaft mounted within said housing, a potentiometer having awiper controlled by rotation of said shaft, means adapted to connectsaid potentiometer in controlling relation to the electrical controlmeans, an override mechanism mounted on said shaft, a snap-on mechanicalconnection mounted on said override mechanism, said override mechanismfunctioning to limit the rotation of said shaft and said potentiometerwiper as said snap-on connection rotates, a follower member adapted tocooperate with generally horizontal datum means, means removablymounting said follower member on said snapon connection, and furthercircuit means adapted to be electrically connected through said snap-onconnection when said follower member is mounted thereon.

8. A follower sensor for use with a road paving machine having agenerally vertically movable screed assembly to form a generallyhorizontal road surface, and having electrical control means to controlthe vertical position of a portion of the screed assembly; a housingadapted to be mounted to move vertically as the portion of the screedassembly moves, a rotatable shaft mounted within said housing, apotentiometer having a wiper controlled by rotation of said shaft, meansadapted to connect said potentiometer in controlling relation to theelectrical control means, an override mechanism mounted on said shaft, amechanical snap-on connection mounted on said override mechanism, saidoverride mechanism functioning to limit the rotation of said shaft andsaid potentiometer wiper as said snap-on connection rotates, a followermember comprising a rod defining a center of rotation and includingmechanical means cooperating with said snapon connection to removablymount said rod on said snapon connection, said follower member includinga first portion connected to said rod and spaced therefrom and adaptedto engage generally horizontal datum means to effect rotation of saidrod, said follower member including a wind compensation counterweightportion connected to said rod and spaced therefrom on the opposite sidefrom said first portion, means removably mounting said follower memberon said snap-on connection, and further electrical circuit means adaptedto be electrically actuated when said follower member is mounted on saidsnap-on coupling.

References Cited by the Examiner UNITED STATES PATENTS 1,481,322 1/24Kellum 338- 1,645,654 10/27 Lorentzen 338-165 2,423,603 7/47 McCandless338-165 2,502,217 3/50 Guibor.

2,518,332 8/50 Keegan et al. 338-165 2,844,882 7/58 Earley 94-46 X2,864,452 12/58 Guntert.

3,029,715 4/62 Bowen 94-46 3,029,716 4/62 Shea 94-46 3,111,070 11/63Pollitz 94-46 CHARLES E. OCONNELL, Primary Examiner.

JACOB L. NACKENOFF, RICHARD W. COOKE, JR.,

Examiners.

2. A FOLLOWER SENSOR FOR USE WITH A ROAD PAVING MACHINE HAVING A MOVABLEPAVING INSTRUMENTALITY ADAPTED TO BE CONTROLLED IN ACCORDANCE WITH APRE-ESTABLISHED DATUM, AND HAVING; ELECTRICAL CONTROL MEANS HAVINGOUTPUT MEANS ADAPTED TO CONTROL THE POSITION OF THE INSTRUMENTALITY,COMPRISING; A HOUSING ADAPTED TO BE MOUNTED ON THE MACHINE AND TO BEMOVABLE WITH MOVEMENT OF THE INSTRUMENTALITY, A SHAFT ROTATABLY MOUNTEDWITHIN SAID HOUSING, A POTENTIOMETER HAVING A MOVABLE WIPER CONNECTED TOSAID SHAFT AND MOVABLE THEREWITH, MEANS ADAPTED TO CONNECT SAIDPOTENTIOMETER IN CONTROLLING RELATION TO THE ELECTRICAL CONTROL MEANS, ASNAP-ON MECHANICAL COUPLING MOUNTED ON SAID SHAFT, A FOLLOWER SENSORMECHANICALLY MOUNTED ON SAID SHAFT BY VIRTUE OF SAID SNAP-ON COUPLING TOFACILITATE THE ACCIDENTAL STRIKING AND MECHANICAL DISENGAGEMENT OF SAIDFOLLOWER SENSOR, SAID FOLLOWER SENSOR BEING ADAPTED TO FOLLOW THE DATUMTO CAUSE ROTATION OF SAID SHAFT AND A RESULTING MOVEMENT OF THEINSTRUMENTALITY AND SAID HOUSING, AND FURTHER ELECTRICAL CIRCUIT MEANSINCLUDING SAID SNAP-ON COUPLING AND EFFECTIVE TO BE ELECTRICALLYACTUATED UPON ACCIDENTAL DISENGAGEMENT OF SAID FOLLOWER SENSOR.